Carbon dioxide as an alternative solvent for the direct synthesis of hydrogen peroxide: A review of recent activities

Fenton/Fenton-like processes with in-situ production of hydrogen peroxide/hydroxyl radical for degradation of emerging contaminants: Advances and prospects

Fenton processes based on the reaction between Fe²⁺ and H₂O₂ to produce hydroxyl radicals, have been widely studied and applied for the degradation of toxic organic contaminants in wastewater due to its high efficiency, mild condition and simple operation. However, H₂O₂ is usually added by bulk feeding, which suffers from the potential risks during the storage and transportation of H₂O₂ as well as its low utilization efficiency. Therefore, Fenton/Fenton-like processes with in-situ production of H₂O₂ have received increasing attention, in which H₂O₂ was in-situ produced through O₂ activation, then decomposed into hydroxyl radicals by Fenton catalysts. In this review, the in situ production of H₂O₂ for Fenton oxidation was introduced, the strategies for activation of O₂ to generate H₂O₂ were summarized, including chemical reduction, electro-catalysis and photo-catalysis, the influencing factors and the mechanisms of the in situ production and utilization of H₂O₂ in various Fenton/Fenton-like processes were analyzed and discussed, and the applications of these processes for the degradation of toxic organic contaminants were summarized. This review will deepen the understanding of the tacit cooperation between the in situ production and utilization of H₂O₂ in Fenton process, and provide the further insight into this promising process for degradation of emerging contaminants in industrial wastewater.

Highly Active, Selective, and Stable Direct H2O2 Generation by Monodispersive Pd-Ag Nanoalloy

Hydrogen peroxide (H₂O₂), a green oxidant, has wide applications in various chemical syntheses and is also a promising candidate to replace the traditional toxic oxidants. The direct synthesis of H₂O₂ from H₂ and O₂ is a potential approach, as it is a green and atomically economic reaction. However, the most previous systems are notorious in complicated post-purification procedures, high energy cost, and low selectivity because of the uncontrollable O-O bond cleavage. We have solved this challenge by tuning the chemical state of Pd with high H₂O₂ productivity of 80.4 mol kg_cat^-1 h^-1 and high H₂O₂ selectivity of 82.1% via the design of Pd-Ag nanoalloys with flexibly tuned size and composition. The created Pd-Ag nanoalloy also exhibits excellent stability with limited performance decay over recycles. The X-ray photoelectron spectroscopy analysis confirms the electron transfer from Ag to Pd, which generates more Pd⁰ and enables improved H₂O₂ productivity. The theoretical calculation shows that the incorporation of Ag into Pd is beneficial for the stabilization of O₂^2- and the cleavage of H₂ for the enhanced H₂O₂ generation. In addition, the enhanced H₂O₂ desorption on Pd-Ag nanoalloy is beneficial for releasing H₂O₂, which results in the increased H₂O₂ selectivity.

Biorefineries of carbon dioxide: From carbon capture and storage (CCS) to bioenergies production

Greenhouse gas emissions have several adverse environmental effects, like pollution and climate change. Currently applied carbon capture and storage (CCS) methods are not cost effective and have not been proven safe for long term sequestration. Another attractive approach is CO2 valorization, whereby CO2 can be captured in the form of biomass via photosynthesis and is subsequently converted into various form of bioenergy. This article summarizes the current carbon sequestration and utilization technologies, while emphasizing the value of bioconversion of CO2. In particular, CO2 sequestration by terrestrial plants, microalgae and other microorganisms are discussed. Prospects and challenges for CO2 conversion are addressed. The aim of this review is to provide comprehensive knowledge and updated information on the current advances in biological CO2 sequestration and valorization, which are essential if this approach is to achieve environmental sustainability and economic feasibility.

A review on research progress in the direct synthesis of hydrogen peroxide from hydrogen and oxygen: noble-metal catalytic method, fuel-cell method and plasma method

The direct synthesis of H₂O₂ from H₂ and O₂ using Pd catalyst, fuel cell and plasma methods have been reviewed systematically.